Messrs. Gladstone and Tribe on an Air-battery. 



63 



Time after 

 immersion. 



Expt. I. 



Expt. II. 



Oxygenized. 



Deoxygenized. 



Oxygenized. 



Deoxygenized. 



1 minute. 



4 minutes. 

 12 „ 

 49 „ 



78 

 72 

 68 



14 

 9 

 6 



130 



90 



75 

 58 



11 

 8 

 6 

 3-5 



The contrast is evident. That the deoxygenized solution does 

 give a deflection at all is due partly to the difficulty of excluding 

 air, and partly, perhaps, at first to the oxygen condensed on the 

 surface of the silver plate. The effect due to the water itself is in- 

 appreciable. 



From the nature of the reaction it might be expected that the 

 current would gradually diminish on account of the using up of 

 the dissolved oxygen in the neighbourhood of the silver ; such a 

 diminution always does take place, at least after the first few vi- 

 brations of the needle. 



It might be expected, too, that when the amount of action has run 

 down considerably, the mere moving of the liquid so as to bring 

 fresh parts of the solution against the silver would augment the 

 currents. It does so. 



The same might be predicted from stirring up the crystals of 

 silver in the tray so as to expose new surfaces. This also was found 

 to be the case. 



And, again, it might be anticipated that if the wire were discon- 

 nected for a time so as to allow the oxygen to diffuse itself from 

 other parts of the solution, and the connexion were made, the cur- 

 rent would be found as strong, or nearly so, as before. That also 

 is true in fact. 



A cell with the plates connected by a wire was placed under a 

 bell-jar full of air over mercury. The mercury gradually rose 

 inside, as might be expected from the absorption of the oxygen in 

 the air. 



The necessity of oxygen and the avidity with which it is taken 

 up are both illustrated by the following experiment : — Two cells 

 with horizontal plates were prepared alike in every respect, except 

 that the first was filled with a solution simply deprived of oxygen, 

 the second with a solution through which a stream of carbonic-acid 

 gas had been passed for some time. The first was placed in the 

 air, the second in a vessel from which the air had been expelled 

 by allowing carbonic-acid gas to flow into it for an hour or two. 



The deflections obtained were as follows, the 1-999 shunt being 

 used and the temperature being 13°- 7 C : — 



